Refrigerating apparatus



Nov. 24, 1936. L. E. SMITH 2,051,599

' I REFRIGERATING APPARATUS Filed 001 19, 1934 Patented Nov. 24, 1936UNITED STATES PATENT OFFICE,

REFRIGERATING APPARATUS Lloyd E. Smith, Dayton, Ohio, assignor toGeneral Motors Corporation, Dayton, Ohio, at corporation of DelawareApplicationOctober 19, 1934, Serial No. 749,055

18 Claims.

' scription, reference being had to the accompanying drawing, wherein apreferred form of the present invention is clearly shown.

In the drawing:

The figure represents diagrammatically an apparatus embodying features01 my invention.

In practicing my invention, a refrigerant liquefying unit I is connectedwith a plurality of evaporators ll, Na, and ill) in refrigerant-fiowrelationship. The evaporators Ii, Ha, and lib are so constructed thatthey are likely to impose varying refrigeration loads on the refrigerantliquefying unit it.

The unit ill, which is operated by a motor l3, tends to have arelatively constant refrigerating capacity while the evaporators Ii, Hoand Nb may be connected to the unit it simultaneously or in timestaggered relationship. This tends to create an unbalanced conditionbetween the capacity of the unit ill and the evaporators ll, Ma

and lib. Controls are provided for balancing these capacities.

The refrigerant liquefying unit has a refriga erant low pressure sideand a refrigerant high pressure side. Thus it may include a compressorI4 and a condenser M which is provided with a refrigerant receiver H5.The compressor M is provided with an evaporated refrigerant inlet Hwhich forms part of the refrigerant low pressure side, and is connectedby a discharge conduit ill with the condenser l5 which forms a part ofthe high pressure side.

The high pressure side is connected by a liquid refrigerant line is withthe evaporators ll, Illa and lib which latter are provided with valvemeans at their inlets to control the flow of liquid refrigerant into theevaporators. The evaporators are also connected by an evaporatedrefrigerant line with the liquefying unit Ill thus forming the lowpressure side of the system.

The valve means for the evaporators ll, Illa and lib may includeautomatic expansion valves 2i, 2 la and 2 lb which are of the characterwhich automatically introduced refrigerant into the evaporators when thepressure therein is reduced below a predetermined limit. These expansionvalves preferably are also provided with thermostatic bulbs 23, 23a and23b which automatically throttle the flow of liquid refrigerant into theevaporators in accordance with temperature conditions in a portion ofthe evaporators preferably located at the outlet of the evaporators. Theconstruction and operation of these valves therefore is such that whenthe pressure in the evaporators is reduced below a predetermined limitthey introduce liquid refrigerant into the evaporators unt'ifth'erefrigerating effect thereof reaches the bulbs 23, 23a and 2312, afterwhich the valves throttle the fiow of refrigerant into the 'evap'oratorsto prevent the waste of refrigeration the thermostats 27, 21a and 27b,placed in the rooms 29, 29a and 2%, respectively, in which theevaporators are placed, open and shut the valves 25, a and 25b inaccordance with air temperature conditions in the rooms 29, 29a, and29b;

The evaporators ll Ma and Nb may be of any suitable construction; but inthe preferred form, they form parts of air conditioning for coolingequipment. Thus they may be placed in casings M, Ma. and MI) throughwhich a circulation of air is forced by means of motor-driven fans 33,

- valves 25, 25a and 25b. Under such conditions,

the amount of refrigeration required by the remaining evaporator orevaporators is materially reduced, while the capacity of the unit Illtends to remain constant. Under such conditions the unit I0 would tendto reduce the refrigerant temperature in the remaining active evaporatoror evaporators below the acceptable temperature. In the use ofrefrigerant evaporators for air conditioning, it is desirable tomaintain the cooling surfaces of the evaporators above the freezingtemperature of water, so that the cooling surfaces do not accumulatefrost but merely condense the moisture from the air and permit it toflow away. When the capacity balance of the system is thrown off by theinactivity of one or more of the evaporators, the excess capacity of theunit l0 tends to reduce the temperature of the active evaporators to toolow a temperature. This invention prevents this undesirable result.

Accordingly, means are provided for throttling the flow of refrigerantinto the liquefying unit Ill when the pressure of the refrigerant fromthe evaporators falls below a predetermined or desirable limit and thusthe temperature of the evaporators is prevented from falling below aselected limit, such as 32 F. This means takes .the form of anautomatically actuated valve means 40 which is actuated by pressureresponsive means or bellows 4| in accordance with thetemperature-pressure conditions in the evaporated refrigerant line 20.As the pressure in line'20 falls to a temperature-pressure conditionnear the freezing point of water, the bellows 4| expands by the actionof atmospheric pressure through the opening 42 on one side and therefrigerant pressure in the chamber 43. The expansion of the bellows 4|raises the valve rod 41 through the medium of the lever 44, which ispivoted at 45 and engages the pin 46 of the rod 41. When the valve 40 isthus raised, the flow of refrigerant in the low pressure side of theapparatus is throttled to prevent a drop in temperature of the activeevaporators below the freezing point of water. The temperature-pressurelimit at which the valve 40 closes in response to the action of thebellows 4| is chosen to be below the pressure-temperature conditions atwhich the valves 2|, 2m and 2H) open. I

In the manufacture of refrigerating apparatus for air conditioning, itis quite usual to assemble the refrigerant liquefying unit as one pieceof mechanism, and each of the evaporators H a and lb, etc., togetherwith their casings, fans, valves, etc., as other pieces of mechanism.These factory assembled pieces of mechanism are shipped to the placewhere they are to be installed and there they are assembled foroperation. It frequently happens that the Wrong number of evaporatorsare connected to a refrigerant liquefying unit. Sometimes the numberactually installed is less than the proper amount for correctrefrigeration balance and at other times the number of evaporators ismore than the proper amount for correct balance. When less than theproper amount are installed, the valve 40 when actuated by the bellows4| will prevent the unit I 0 from producing too low temperatures in theevaporators installed, and this invention is therefore applicable alsoto installations where the wrong number of evaporators are installedeven when the evaporators are not independently out out.

In order to take care of the condition when too many evaporators areinstalled, means are provided to throttle the low pressure side when thepressure-temperature conditions in the evapora-- tors rise above apredetermined limit due to the presence of an excess number ofevaporators. Either an additional valve, or the same valve 40 may beused for this purpose. If the valve 48 is used, a pressure responsivemeans in the form of bellows 48 is connected to the valve 40 through themedium of rod 41, pin 49 and lever 50 pivoted at 5|. When thepressure-temperature conditions in the line 28 and chamber 43 rise abovea predetermined limit, the bellows 48 tends to col- 21a and 211)effective.

lapse because of the increased pressure differential between the chamber43 and .the atmospheric pressure in bellows 48 entering through theopening 52. When the bellows 48 thus collapses the valve 48 risesandthrottles the flow of refrigerant to the unit l0 and thus prevents itfrom being overloaded.

It sometimes occurs that the refrigerant pressure on the high sidebecomes excessive, for instance when the flow of cooling medium to thecondenser 5 is accidentally prevented. Means are provided for reducingthe capacity of the unit I0 under these conditions and this may beaccomplished by providing means for throttling the flow of refrigerantfrom the low pressure side to the unit l0 when these conditions occur.This may be accomplished either by an additional valve or by the samevalve 40. Thus a rod 53 may be actuated by the bellows 54 which is Ct.rnected on one side by the pipe 55 with the high pressure side and withthe atmosphere through the opening 56 on the other side. When thepressure becomes excessive on the high pressure side the rod 53 risesand throttles the valve 40.

It is to be understood that the bellows 4|, 48 and 54 may be eachindependently connected to an individual valve rather than all beconnected to a single valve. Adjusting screws 51 and 58 may be providedto vary the tension of the springs 59 and 60 respectively so that thepressure conditions at which the bellows 4| and 48 operate may beadjusted. A small bellows 6| may be provided to prevent the escape ofrefrigerant through the opening 56, and spring means 62 may be providedto properly calibrate the action of the bellows 54.

If the refrigerant liquefying unit is manufactured as an entity at thefactory it is often desirable to assemble the valve structure containedin the casing 63 with the refrigerant liquefying unit, thus insuringsatisfactory operation of the unit l0 even if the same should beassembled with the wrong number of evaporators.

An automatic control may be provided for the unit Hi. This may take theform of a snap switch 64, operated by a bellows 65 in response toconditions of the apparatus, such as in response to the refrigerantpressure at the intake transmitted through the pipe 66 to the bellows 65thus starting and stopping the unit ID as refrigerant conditionsrequire.

Means are provided for permitting the fans 33, 33a and 33b to beoperated when refrigeration is not desired and for insuring theoperation of these fans when there is a refrigeration demand upon theirrespective evaporators. These means are preferably coordinated with thethermostats 21, 21a and 21b and with the switch 64 to insure that theunit I 0 shall not operate for appreciable periods of time when all ofthe evaporators are rendered inactive but shall operate in response topressure conditions when any one of the evaporators is rendered active.

Thus hand switches 69, 69a and 692) are provided which may cause theoperation of the respective fans 33, 33a and 331) when air circulationis desired even when refrigeration is not desired. The closing of theseswitches energize the respective fan motors from source 39. Handswitches 10, 10a and 10b are also provided for rendering the refrigerantcontrol thermostats 21, When any of the switches 70, 1011 or 10b aremanually closed the corresponding thermostat is rendered capable ofenergizing its corresponding relay 61, 61a or 61b.

The energizing of any of the relays 61, 61a or 61b in turn closes itscorresponding switch 68, 58a or 68b which in turn energizes and opensits corresponding solenoid valve 25, 250. or 25b.

The above electrical controls therefore cause the unit I to maintain therefrigerant pressure in. suction line 20 between the lowest pressurelimit for which bellows M is calibrated and the highest pressure limitfor which switch 64 is calibrated. The low pressure limit of the switch64 is made lower than the low pressure limit of the bellows II so thatwhen the-bellows 4| throttles the valve 40 a certain amount the bellows65 closes the switch 64. The unit It therefore maintains the suctionline 20 in readiness to evaporate refrigerant in any one of theevaporators II, II a or llb whenever the corresponding valve 25, 25a or25b is opened. When any one or more of the switches 10, 'llla or 70b areclosed then the corresponding thermostat 21, 2101. or 211) feedsrefrigerant into its corresponding evaporator I I, Ila or lib inresponse'to the temperature in its corresponding room. This provides thenecessary refrigeration for each room as it is required. At the sametime the proper evaporator temperatures are maintained so that nodeleterious frosting thereon occurs.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows: 1. Refrigerating apparatus comprising arefrigerant liquefying unit having a refrigerant low pressure side and ahigh pressure side, a

frigerant liquefying unit having a refrigerant low pressure side and ahigh pressure side, a plurality of evaporators having refrigerant inletsconnected to said high pressure side and refrigerant outlets connectedto said low pressure side, throttling means on said low pressure sideeffective to throttle the flow of refrigerant into said li uefying unitwhen the pressure of the refrigerant from said evaporators falls below apredetermined limit and when the refrigerant pressure in said highpressure side rises above a predetermined limit.

3. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, throttling means on said low pressure side effective tothrottle the flow of refrigerant into said liquefying unit when thepressure of the refrigerant from said evaporators rises above apredetermined limit and when the refrigerant pressure in saidhighpressure side rises above a predetermined limit.

4. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets'connected to saidhigh pressure side and refrigerant outlets rises above a predeterminedlimit.

5. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, expansion valves at said inlets having means forautomatically introducing refrigerant into said evaporators when thepressure in said evaporators is reduced below a predetermined limit,throttling means on said low pressure side effective to throttle theflow of refrigerant into said liquefying unit when the pressure of therefrigerant from said evaporators falls below a predetermined limit andwhen it rises above a predetermined limit.

6. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, expansion valves at said inlets having means forautomatically introducing refrigerant into said evaporators when thepressure in said evaporators is reduced below a predetermined limit, andhaving means for throttling the flow of refrigerant into saidevaporators in accordance wi h temperature conditions in a portion ofsaid evaporators, throttling means on said low pressure side effectiveto throttle the flow of refrigerant into said liquefying unit when thepressure of the refrigerant from said evaporators falls below apredetermined limit and when it rises above a predetermined limit.

7. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, valves at the inlets of said evaporators responsive totemperature conditions of air cooled by said evaporators,

throttling means on said low pressure side effec-- tive to throttle theflow of refrigerant into said liquefying unit when the pressure of therefrigerant from said evaporators falls below a predetermined limit andwhen it rises above a predetermined limit.

8. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality .of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, electro-magnetic valves for said evaporators having meansfor electrical energization in accordance with conditions produced bysaid evaporators, throttling means on said low pressure side effectiveto throttle the flow of refrigerant into said liquefying unit when thepressure of the refrigerantfrom said evaporators falls below apredetermined limit and when it rises above a predetermined limit.

9. Refrigerating apparatus comprising a compressor, condenser andrefrigerant evaporating means, an evaporated refrigerant line connectingsaid evaporating means and the intake of said compressor, a liquidrefrigerant line-connecting said condenser and said evaporating means,throttling means in said evaporated refrigerant line effective tothrottle the flow of refrigerant into gle valve in said evaporatedrefrigerant line effective to throttle the flow of refrigerant into saidcompressor when the refrigerant pressure in said evaporated refrigerantline falls below a predetermined limit and when the refrigerant pressurein said condenser rises above a predetermined limit.

11. Refrigerating apparatus comprising a compressor, condenser andrefrigerant evaporating means, an evaporated refrigerant line connectingsaid evaporating means and the inlet of said compressor, a liquidrefrigerant line connecting said condenser and said evaporatingmeans,throttling means in said evaporated refrigerant line effective tothrottle the flow of refrigerant into said compressor when therefrigerant pressure in said evaporated refrigerant line rises above apredetermined limit and when the refrigerant pressure in said condenserrises above a predetermined limit.

12. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, automatic expansion valves at said inlets, throttlingmeans on said low pressure side effective to throttle the flow ofrefrigerant into said liquefying unit when the pressure of therefrigerant from said evaporators falls below a predetermined limit andwhen the refrigerant pressure in said high pressure side rises above apredetermined limit.

13. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, expansion valves at said inlets having means forautomatically introducing refrigerant into said evaporators when thepressure in said evaporators is reduced below a predetermined limit,throttling means on said low pressure side effective to throttle theflow of refrigerant into said liquefying unit when the pressure of therefrigerant from said evaporators falls below a predetermined limit, andwhen the refrigerant pressure in said high pressure side rises above apredetermined limit.

14. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, expansion valves at said inlets having means forautomatically introducing refrigerant into said evaporators when thepressure in said evaporators is reduced below a predetermined limit, andhaving means for throttling the flow of refrigerant into saidevaporators in accordance with tem- V perature conditions in a portionof said evapor ators, throttling means on said low pressure sideeffective to throttle the flow of refrigerant into said liquefying unitwhen the pressure of the refrigerant from said evaporators falls below apredetermined limit and when the refrigerant pressure in said highpressure side rises above a predetermined limit.

15. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, valves at the inlets of said evaporators responsive totemperature conditions of air cooled by said evaporators, throttlingmeans on said low pressure side effective to throttle the flow ofrefrigerant into said liquefying unit when the pressure of therefrigerant from said evaporators falls below a predetermined limit, andwhen the refrigerant pressure in said high pressure side rises above apredetermined limit.

16. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, electro-magnetic valves for said evaporators having meansfor electrical energization in accordance with conditions produced bysaid evaporators, throttling means on said low pressure side effectiveto throttle the flow of refrigerant into said liquefying unit when thepressure of the refrigerant from said evaporators falls below.apredetermined limit, and when the refrigerant pressure in said highpressure side rises above a predetermined limit.

17. Refrigerating apparatus comprising a refrigerant liquefying unithaving a refrigerant low pressure side and a high pressure side, aplurality of evaporators having refrigerant inlets connected to saidhigh pressure side and refrigerant outlets connected to said lowpressure side, automatic expansion valves at said inlets, throttlingmeans on said low pressure side effective to throttle the flow ofrefrigerant into said liquefying unit when the pressure of therefrigerant from said evaporators rises above a predetermined limit andwhen the refrigerant pressure in said high pressure side rises above apredetermined limit.

18. The method of operating a refrigeration system which comprisescirculating a volatile refrigerant from a refrigerant liquefying zonethrough a liquid refrigerant conveying zone, through a plurality ofevaporating zones in parallel into a common vapor-conveying zone and tothe refrigerant liquefying zone for recirculation, maintaining theliquefying capacity of said liquefying zone sufficient for the demandsof all of said evaporating zones, periodically stopping the flow ofrefrigerant through one or more of said evaporating zones, automaticallythrottling said vapor conveying zone to maintain the refrigerantpressure in said conveying zone adjacent said evaporating zones abovethe vapor pressure corresponding to 32 F., and automatically throttlingsaid refrigerant conveying zone when its pressure rises above apredetermined limit.

LLOYD E. SMITH.

